The only adjustment you have is the pressure switch. Usually 30/50 with a jet, but you might be able to get 40/60 depending on which model pump you have. You can’t set the booster pump to a pressure. Without a CSV, the pressure from the booster pump will be determined by how much water you are using. No you don’t have to have a CSV. Your pump will just cycle on and off anytime you are not using the maximum flow the pump can produce. But a CSV and a 4 gallon tank would have saved you a lot of money compared to a large pressure tank or two, and the CSV would do a better job than both of those tanks together, and made your pump last longer.